I've got trouble code PO304 on my '02 Escort. I've replaced the spark plugs which were in pretty bad condition, this helped smooth the engine out some, but I still had the PO304 code. Next I alternated the plug wires between 3 and 4 and erased the codes. I took the car for drive to get it to reset a code and the CEL came back on in about 1 1/2 miles, drove the car back home hooked up the code reader and still have PO304. Thus far I've ruled out the possibility of plugs and wires. My next suspected cause is a bad fuel injector, but I don't know how to test them. Can someone tell me how to test the injector? I'm also going to pull the coil off and test it. If anyone has any other ideas of things that could be the cause please post them. Thanks for any assistance!!

Thanks for the link. I see a couple things such as the cam & crank sensors that hadn't even crossed my mind. Hopefully I'll get a chance to look more closely at it tomorrow and do some more trouble shooting. My son drove the car to work a couple days ago and called me from work saying the check engine light had came on about 1/4 mile before he got to work and was flashing, I knew this was an indication of a serious problem. He only works about 4.5 miles from where we live so I told him to drive it straight home after work and I'd start trying to figure it out. Otherwise the car hasn't been driven more than 4-5 miles to check the possibility of a bad wire.

The Chilton's manual tells me the center pin (ignition start/run) going to the coil pack should have 10 volts with the ignition off. I think this is the tach signal wire. I checked it and it was only .1 volt going to it. Any ideas of what to check or what the problem may be other than possibly the wire? If it's in the wiring I'll have to have someone else take a look at it since I'm not very good with electrical gremlins.

Other things I've already checked are compression on #4 (175 PSI) replacing the spark plugs, alternating #3 & #4 plug wires resetting the ECU and drove the car. Code PO304 came back ruling out the plug wires, tested the coil, and tested the cam position sensor, both tested good. I haven't put the spark tester on it, but I don't think #4 is firing. When I took the plug for #4 out to check the compression it was gas soaked so the injector is firing.

I tried moving the #4 wire to the #3 cylinder, but the misfire came back on #4 even with another wire going to the plug. If it were a bad wire the misfire would have moved to #3. The misfire is bad at idle as well as under load.

Would it only have a misfire on one cylinder? The Escort has a waste spark ignition system so it fires two cylinders at the same time, one on the compression stroke and the other on the exhaust stroke. If I remember correctly it fires 1 & 4 at the same time.

After re-reading my previous post I need to clarify. The 10 volts should be on the center pin of the wiring harness with the ignition off not the center pin of the coil. Hopefully now that I've cleared that up it will help.

I'll check the thread again tomorrow and if there's no other suggestions. I might pull the coil off my '97 Escort and put it on the '02 to see if that resolves the problem.

Without a scope, it'd be hard to tell if it was bad or not. The waste spark is fired when on ehaust so that part wouldn't show up. To bad you couldn't get another one to try.

If it were the coil since the same side of the coil also fires #1 is it possible for the coil to be bad and still fire one of the cylinders of that coil on the compression stroke and not the other? I would have thought if the coil was bad it would affect both cylinders it's responsible for, giving me PO301 and PO304. I appreciate your help and I'm not trying to be argumentative just trying to get accurate information.

What I'm trying to say is would it still fire #1 on it's compression stoke even though it doesn't fire #4 on it's compression stroke.